Crossbar switch system with sequentially operated magnets



J. H. VOSS Nov. 4, A'1947.

CROSSBAR SWITCH SYSTEM WITH SEQUENTIALLY OPERATED MAGNETS Filed Nov.y 2l, 1945 6 Sheets-Sheet 1 DIAL TONE lll F JOHN WJQNTOR' ATTOR N EY Nov. 4,11947. J. H.Ivoss 2,430,316

lCROSSBILR SWIvTCH SYSTEM WITH SEQUENTIALLY OPERATED MAGNETS Filed Nov. 21, 1945 6 Sheets-Sheet 2 wlwllff... :Illini -1: l

NVENTOR. JOHN H. voss Arromev n 3 ...0. 6 2 2 -nn/ v l 2n c2043 'i Li: l"

Nav. 4, 1947.A

J. H. Voss CROSSBAR SWITCH SYSTEM WITH SEQUNTIALLY OPERATED MAGNETS Filed Nov. 21, 1945 y 6 Sheets-sheet 5 goo'a Rmsm; C303 INTERRZUPTER INV EN TOR. JOHN H. V055 ATTORNEY NOV. 4, J, H. V055 2,430,316

CROSSBAR SWITCH SYSTEM WITH SEQUENTIALLY OPERATED MAGNETS Filed Nov. 21. 1945 6 Sheets-Sheet 4V C530x INVENTOR.

JOHN H V055 Pf6-4 y AITTOR NEY J. H. VOSS Nov. 4,'1947.

CROSSB'AR SWITCH SYSTEM WITH SEQUENTIALLY OPERATED MAGNETS Filed Nov.' 21, i945 6 Sheets-Sheet 5 if 1 T3653?! Ti-c534 ATTORNEY Nov. 4, 1947. 2,430,316

cRossBAR swITcH SYSTEM WITH SEQUENTIALLY OPERATED MAGNETS J. H. Voss Ameel Nov. 21, 1945 e sheets-sheet s MSq IN V EN TOR.

JOHN H. V055 ATTORNEY Patented Nov. 4, 13947 CROSSBAR SWITCH SYSTEM WITH SEQUEN- TIALLY OPERATED MAGNETS .lohn H. Voss, Downers Grove, Ill., assigner to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application November 21, 1945, serial No. 630,064

Claims.

The present invention relates in general to telephone systems, and in particular to automatic telephone systems which employ switches of the crossbar type to eilect connections.

The objects of the invention are to improve telephone systems of this character through the provision of simplified and more efficient circuit arrangements for directing the operation of the crossbar switches, to reduce the amount of control equipment associated with each switch to a minimum, to reduce the time required to establish connections in such a system, and to eliminate common equipment insofar as practical so as to provide increased reliability oi operation.

The main feature of the invention is the provision of a crossbar switch system wherein the operating magnets of the crossbar switches are operated directly from dial impulses, thereby eliminating the need for separate impulse counting relays and other auxiliary control equipment.

Another feature is the provision of a crossbar switch system wherein the operating magnets of the crossbar switches are employed to perform selecting operations other than, and in addition to, the selection of a line to which the switch has access; such, for example, as selecting the ringing code in accordance with received dial impulses in a party line connector.

Still another feature is the provision of means for first operating a crossbar switch to select a group of lines; and for thereafter causing the switch to automatically hunt for, and establish connection with, an idle line in the selected group.

The foregoing and other features will be described more fully in the following description. Circuits embodying the invention have been shown in the accompanying drawings in which:

Fi-g. 1 discloses the control circuit for a crossbar selector,

Figs. 2, 3 and 4, which should be placed side by side in the order named, taken together disclose the control circuit for a crossbar connector, and

Figs. 5 and 6, which should be placed side by side with Fig. 5 on the left, taken together disclose a lcrossbar switch adapted for use either as a selector or a connector. For use as a selector Fig. 5 should be placed to the right of Fig. 1, and for use as a connector Fig. 5 should be placed to the right of Fig. 4.

The crossbar switch employed in the present system is only schematically illustrated in Figs. 5 and 6. The novel construction and details of operation of this switch are fully described and illustrated in the copending application of K. W.

2 Graybill et al., Serial No. 630,065, filed November 21, 1945.

The invention will first be described briefly, following which a detailed description of the illustrated embodiment thereof will be given. The crossbar switch, schematically illustrated in Figs. 5 and 6, comprises a plurality of contact sets, which are disposed in intersecting rows, and two intersecting groups of selecting members which are arranged to permit selective operation of any of the contact sets through operating members individual thereto. Each selecting member of one group is arranged to move a row of the operating members so that any one of the operating members so moved may be engaged by corresponding ones oi the selecting members in the second group to operate the contact set at the intersection of the two actuated selecting members. Individual magnets are provided for actuating each selecting member in the second group. A common control magnet is provided for operating the selecting members in the first group. This control magnet is normally ineiiective to operate any of the members associated therewith unless one of the selecting magnets is operated, in which case a corresponding finger is moved by the operated selecting magnet so that the control magnet is effective to actuate a selecting member in the rst group which corresponds to the operated selecting magnet. These fingers are arranged so that the control magnet is effective to hold the actuated selecting member in the rst group after the selecting magnet is released. Thus by first operating a selecting magnet, next operating the control magnet, and then releasing the selecting magnet; the selecting member in the rst group corresponding to the operated selecting magnet will be actuated and held by the control magnet. The actuated selecting member moves its associated row of operating members so that a subsequent operation of any of the selecting magnets will operate the contact set located at the intersection of the selecting member in the iirst group held by the control magnet and the selecting member in the second group actuated by the subsequently operated selecting magnet. A latching mechanism is provided which is operated in response to the restoration of the control magnet to hold the actuated selecting member in the second group when the selecting magnet associated therewith is subsequently released. The operated contact set is thus held independently of the selecting and control magnets. The selecting magnets may then be reoperated to perform other switching operations without disturbing the established connection. A common release magnet is provided for releasing the latching mechanism to restore the switch to normal, The selecting magnets are provided with individual contact sets which are interconnected so as to permit sequential operation of the magnets in the manner of a counting chain, whereby the switch may be operated directly from received dial impulses in a step by step manner, and whereby the magnets may be controlled by re-V ceived dial impulses to perform additional selecting functions.

When this novel crossbar switch is employed as part of a selector, the control relays shown in Fig. 1 are associated therewith; and when the switch is employed as part of a connector, the control relays shown in Figs. 2, 3 and 4, are associated therewith. Either of thesevgroups oi control relays may be made accessible to subscribers lines in any well known manner; such, for example, as line finders, plunger lineswitches or rotary lineswitches. Alternatively, the connector control relays may be reached from a selector which may be of the type herein disclosed.

When the selector relays are seized by the extension thereto of a subscribers line from a preceding switch, they prepare circuits for sequentially operating the selecting magnets of the associated crossbar switch under the control of the calling subscribers dial. Upon the termination of a series of impulses, the control magnet of the switch is operated to select a group of lines corresponding to the last operated selecting magnet, which selecting magnet is subsequently released. The selecting magnets are then sequentially operated under the control of the selector relays to nd, and extend the calling line to, an idle line in the selected group. Upon connection with an idle line the control magnet is released, causing the established connection to be held by the latching mechanism. When the calling party hangs up, the release magnet of the switch is operated to release the latching mechanism'and thereby restore the switch to normal.

When the connector relays are seized by the extension thereto of a subscriberis line from a preceding switch, such as the selector just described, they prepare circuits for sequentially operating the selecting magnets of the associated crossbar switch under the control of the calling subscribers dial. Upon the termination of the first series ofimpulses, which determines which one of two groups of ringing codes are to be used, a register relay corresponding to the last operated selecting magnet is operated and the selecting magnet is then released. The selecting magnets of the crossbar switch are then again sequentially operated in response to a second series of impulses from the calling partys dial. At the end of this second series of impulses the control magnet of the' crossbar switch is operated and the last operated selecting magnet is 4released to complete the group selection.` The selecting magnets are then operated in response to a third series of irnpulses to select the desired line in the previously selected group. The control magnet is then restored causing the established connection to be maintained by the latching mechanism of the switch independently of the selecting magnets, which are restored to normal. rlhe selecting magnets are then 'finally `operated in accordance with a fourth series of" impulses to select the code for ringing the called station. When the conversation is completed the latching mechanism is re- 4 leased by the operation of the release magnet yto restore the switch to normal.

The invention will now be described in detail with reference to the accompanying drawings. It will be assumed that the selector and connector switches are connected in tandem and that the selector is associated with a calling subscribers line by means of a line finder such as that shown in Fig. 1 of Patent No. 2,214,908; issued to Lomax et al. The conductors CIIS to CIIB extending from the left of Fig. 1, in the present case connect with the corresponding conductors extending from the right of Fig. 1 in the Lomax patent. No provision is made for a fourth conductor in the Lomax patent, which fourth conductor CI I9 usually extends to make contacts, such as RA|53 and RA |63, on relays R|50 and RI50 of the patent, the armatures of these contact sets extending to wipers, such as |43 and |46, which engage added sets of bank contacts when the finder switch is operated. These added bank contacts may be strapped to ground as desired so that when the iinder switch is associated with certain lines the fourth conductor CI I9 will be grounded to provide a special service or restriction in the succeeding switch train.

I. OPeeArroN or THE SELECTOR A. Group selection in accordance with first digit dialled When the iinder switch associated with the selector relays of Fig. 1 is operated to nd a calling line, it closes a loop circuit over conductors C| IB and CI I'I to relay |80 which operates and closes a circuit to relay |60 at contacts |8I. Relay !00 operates, closes a multiple ground to conductor CIIB at contacts |6| to hold the nder switch after it is released by the finder distributor, closes a circuit to the lower winding of relay H0 at contacts |62, and prepares an impulsing circuit to the crossbar switch magnets and a holding circuit to the upper winding of relay II) vat contacts |64. Relay IIO operates and replaces direct ground on the lower winding of relay with ground through a dial tone transformer, not shown, at conta'cts I I I.

When the preceding finder switch has seized the calling line it is extended to relay |80 over conductors CI I6 and C'I I'I in place of the original seizing loop. Upon 'hearing dial tone transmitted from the selector relays the calling party proceeds to dial the lrst digit of the desired subscribers number, causing relay |80 to be momentarily released a corresponding number of times.V Upon the first restoration of relay |80 a circuit is completed from ground through contacts |98, lilI, |64, |31 and II2 to the upper winding` of relay ||0. A circuit is also completed over a portion of the above traced circuit and through contacts |53, |48, |43 and over conductor C508'to magnet MI (Fig. 5). Magnet MI operates; at contacts MI e prepares its holding circuit over conductor C509, through contacts |41, relay |40, and contacts |33 and |62 to ground; 'and vprepares a circuit =ior operating magnet M2 over conductor C5I2 at contacts Mlf. Upon the irst reoperation of relay |80 a short circuit is removed from relay |40 at contacts I8I, causing this relay to be energized in series with magnet MI. Relay |40` operates, opens the circuit to the lower winding of relay IIE) at contacts |41, and transfers the impulsing circuit from magnet MI tovmagnet M2 over con# ductor C5|2 at contacts' |43. Upon the second restoration od relay I8I`,`magnet M2 is energized Vin multiple with the upper winding of relay through contacts |8|. Magnet M2 operates; at contacts M2e prepares its holding circuit over conductor H), through contacts |52, relay |45, and contacts |34 and |62 to ground; and at contacts MZf prepares a circuit for operating magnet M3 over conductor C5| 3. Upon the second reoperation of relay |80 a short circuit is removed from relay |45 at contacts ISI, causing it to be energized in series with magnet M2. Relay |45 operates, opens the holding circuit to magnet MI through relay |40 at contacts |41 causing them to restore, and transfers the impulsing circuit from magnet M2 to magnet M3 over conductor C5|13 at contacts |48. Upon the third restoration of relay |80, magnet M3 is operated and subsequently held in series with relay |50, which operates when relay |80 reoperates. The operation of relay |50 opens the holding circuit to maget M2 through relay |45 at contacts |52 causing them to restore, and trans fers the impulsing circuit from magnet M3 to magnet M4 over conductor C5|4 and contacts M31c at contacts |53. lt should now be apparent that the fourth restoration of relay |30 will cause magnet M4 to operate and hold in series with relay |40 when relay |30 reoperates. The operation of relay |50 opens the holding circuit to magnet M3 through relay |50 at contacts |42 causing them to restore, and prepares a circuit to magnet M5 over conductor C5|2 at contacts |43. The subsequent restoration-of relay |50 results in the transfer of the impulsing circuit from magnet M4 to magnet M5 at contacts |53. In this manner the magnets M| to M0 are sequentially operated by successive restorations of relay |80. Relays |60 and ||0 are both rendered slow to release by means of copper sleeves so that they will remain operated during impulsing. Assuming that the rst digit in the desired number is 9, magnet M9 will be operated in series with relay |50 after the ninth reoperation of relay |00. Relay ||0 restores shortly after the termination of the series of impulses, reconnects direct ground to the lower winding of relay |80 at contacts and closes a circuit to relay |30 at contacts ||3 from ground through contacts |5| and |62. Relay |30 operates, closes its holding circuit through relay |55 at contacts |3|, and closes a circuit to relay |20 in multiple with control magnet CM over conductor C5|8 at contacts |35. It may here be noted that the contacts on relay |20 are preferably operated by the control magnet CM, but have here been illustrated as being on a separate relay for convenience. Control magnet CM operates and causes finger F9, which is operated by magnet M9, to engage rank selecting member RS9 and shift itk so as to permit the contact operating members associated therewith to fall into slots in corresponding ones of the file selecting members, such as FSI. Relay |20 operates and opens the holdin-g circuit to magnet M3 through relay |50 at contacts |23. Magnet M9 and relay |53 restore. Finger F9 is shaped so that it is held operated and holds rank selecting member RSS operated independently of magnet M9. The restoration of relay |50 removes a short circuit from relay |55 at contacts |5| causing it to be energized in series with relay |39.

B. Selector trunk hunting Relay |55 operates and closes a circuit from ground through contacts |62, |5, |46, |4l, |32, |55, |51 over conductor C5l5, and through Chain tacts contacts, such as M2d, on magnets M2 to M0 to magnet Ml. Magnet Mi operates; closes a circuit from ground over a portion of the last traced circuit, through contacts |01 and |01, over conductor C5|5, and through chain contacts, such as M25, on magnets M2 to M0 to magnet M2 at contacts MIb; and operates le selecting member FSI to cause contact operating member K9| to press its associated Contact set 9| into engagement with the multiple conductors positioned adjacent thereto and represented by small circles. Each of these sets of four multiple conductors extend to a corresponding connector over conductors such as C20| to C204 (Fig. 2). Alternatively, these multiple conductors may extend to a second selector. If the first connector in the 900 group is idle there will be resistance battery on the control lead, such as C205, extending therefrom, while if this connector is busy the control lead will be grounded. The control lead is extended through contact set 3| to conductor C501 which extends through contacts |12, relay |85, and contacts |53 to ground.y Assuming that the first connector is busy, relay will not be energized. Magnet M2 operates over the previously traced circuit, locks to ground over conductor C5|5 through break contacts on all succeeding selecting magnets and its preliminary make contacts M2c, opens the circuit to magnet MI at contacts Mild, closes a circuit to magnet M3 from ground over conductor C5|5 at contacts M2b, opens the circuit between conductor C501 and contact set 9| at contacts M2a, and operates file selecting member FB2 to operate contact set 92. Assuming that the connector associated with the multiple conductors engaged by Contact set 92 is idle, relay |85 will be energized from the resistance battery extended over the control lead of the connector, through contact set 92, contacts such as M3C on magnets M3 to M0, over conductor C501, through contacts |12, relay |85, and through contacts |53 to ground. Relay |95 operates, closes a circuit to relay at contacts |85, and opens the circuit to magnet M3 at contacts |81 before this magnet has time to operate. By this time magnet MI will have restored. Relay |90 operates; transfers the calling party's line extended over conductors CHS and Clll from relay |30 to relay 200 in the connector at contacts I3! and |92, over conductors C502 and C504, through contact set 92, and over the multiple conductors engaged thereby to conductors 020| and C202, thence through contacts 21| and 212 to relay 200; extends the fourth conductor CHS to conductor C203 of the connector over conductor C505 and through contact set 92 at contacts |93; extends ground through con- |6| and |94, over conductor C501, and through contact set 92 to conductor C204 to mark tlhe connector busy to other selectors; closes its locking circuit to ground through contacts |6| at contacts |95; opens the circuit to magnet CM and relay |20 at contacts |95; and opens the circuit to relay |50 at contacts |98. Since each magnet is operated for a brief time after the next succeeding magnet is operated during trunk hunting, separate conductors are multipled to the odd and even numbered contact sets. Thus conductors C50|, C503 and C505 extend to Contact sets 9|, 93, 95, etc., while conductors C502, C504 and C505 extend to contact sets 92, 94, 96, etc. These two groups of conductors are separated except when relay i90 is operated to prevent momentary connections be- |55 and magnet 'SM2 restore. [|90 will lbe .the only relay operated. Also yall `magnets. in: .the crossbar switch will .,be4 restored, the operated contactfset .f92abeing. held.rnechani andopens circuits. to relays |;;.andz|55 in series and magnetMZ atzcontactsiGZ. Relays|30 Aand -At this K.time yrelay cally by the latching mechanism.

C. -Releaseof ,selector Relays 12.0, :|80

The connection .is now extended fbythe .':con-

nector underV the-control of -the,subscribers dial Vas will subsequently be ,described. .After Athe :callis terminated :the iloop gcircuitto the ;conlnector willbe :opened causing it-to releaseand :remove the vground extended Lover conducton e501 from the control f conductor :c2104 if tthe connector. '.Relay i |90 -then restores -and vcloses a `circuit tomagnetxRMgover conductor C5| 9 at `,contactsI-il. AMagnetfRlVl' operates to-release thel latching: mechanismiandtthereby permit le @selecting memberfFS2 5to'y restore: yandl open` contactfset: 92. When Vthe .1 latching f mechanism restores 'the Acircuit to ',magllet `RMris-:Opened zat contacts I.

5D. A'lltrun'lcs busy In the event-,that-rall of;the connectorsassociatedI with contactsets-S |1 to 90 arebusy; magnets 'Ml toMil will befsequentially operated as should be apparent `'from the preceding description.

Vi/'hen-.magnetMiloperates itcloses a circuitto relay |10. over conductor 1,65 ,at :contacts :M012

Afrom groundover conductorGiat-.the sa-me time. that it extends thecontrol conductorfofits associated connector to. relay *|85 over conductor .C507 and through. contact seh-00. iRelay |'|0 is slower vto operate than. relay; |85. ':Gonseq11ently,

;if this. connector isfreerelay |85 operatesand extends the `calling lineto the .connector-in the `previously described '.rnanner. 'The operation of relay |85 also opensthe circuitto relay Ilat contactslSl toprevenooperation/thereof. '.If

lthis IVlast/connector is-busy, relay A185 .will not be energized but relay |'|-0now will-operate and s-ubstit-uteground thro-ugha xbusy Itone tr-ans-l `former, not-shown, for direct groundy on the lower tol prevent operation-thereof in casethe convnector subsequently'becomes free, a-ndopen the circuits to control `-magnet'GM vand relay |20 at contacts |13 causing them torestore. -When Vthe calling vpartyfdisconnectsini-response tothe busy tone the loop circuit toy relay |80'is opened.

|60 at contacts |8|. LRelay |0rrestores;removes ground from conductor 'CI-iwat'contacts IGI to release' the-preeeding finder switch; 'opens the circuits tofrelays |130 `:and"| 55-in seri-es, relay; 'i1-il,

" Relay i'restores-'and opens theI circuit to relay..

and magnet `M0- at-contacts |52; andclosesfay circuit to release magnet RM overiconductor'C 9 vat contactsffl. Relays 1x30, |255, and .|10 restore. lMagnet M0 restores.

"Magnet RM operatesvand releases the latchingf-:mechanism'- to Y perm-it Jiile `selecting member FSO to restoreto complete the' 1 connector relays. iRelay |40 operates. .Mi operates; closes its holding circuit through contactsMie, over conductor C509, through convtherpreceding description of the selector.

weil. gzed depending on whether a 12v ora "3 was dialled. Assuming that-the digit was 2jJ vrelay Yrestoration of the s elector'tonorrnal. When the latChing. mechanismv restores the circuit to i mag- ;net RM is opened ,at contacts 50|.

-II. OPERATION oF THE CONNECTOR A. Selection of ringing code group When the connector is seized by 'a preceding selector as just described, or b y a preceding nder switch, the calling partys line is extended to relay,200 over conductors C20| and C202. It

.may here be noted `that the lower winding of relay200 is vshown connected through contacts 3| and-.l'to ground through a dialtone trans- `former, not shown. -seized from a preceding selector the dial tone is `not required and these contacts may thenbe vWhen the connector is omitted and direct ground connected to the lower winding of relay 2&0. Relay 200 operates and closes a circuit to relay'2l0 at contacts 20|. Relay-2|!) operates and grounds control con- .ductorCZGll at contacts.2|| to hold the preceding. switch train and to mark-the connector busy.

r'.Lhegiirst dialled digit received by the connector will` be either a .2 or a 3. Upon therst restoration of .relay 20% a circuit is completed from ground through contacts 218, 20|, 2|li, and 42| torelay-l. A circuit is also completed in multiple with relay i156 through contacts 492, 482, 412, .and 4521, 4and over conductor C508 tomagnet MI vof the crossbar switch associated with the Magnet tactszll, relay 410, contacts |562, lill, 40|, 22|, .andt2i5 to groundiand prepares a circuit for operating magnet M2 over conductor C5|2 at .contacts M f. 'Upon the first reoperation of relay a .short circuit is removed from relay.l|l0 at contacts 20H causing it to be energizedin series .with-magnet Mi. vRelay ll operates and trans- .fers the impulsing circuit from conductor C508 to conductor C5|2 at contacts'lilZ. The succeeding .operations of the selecting magnets and relays M0 to-l90 in response to successive restorations of relay Sie@ should be-apparent'from Relays 2li) and M0 remain operated during impulsing due to the use of copper sleeves on their which :render them slow to release. Shortly `aiter the series of impulsesis completed relay M0 restores and closes a circuit from .ground through contacts 2|5, over conductor C523, through contacts Mh or Mlm, over conductorC52l,vtlirough contacts 501,440, and.l3|2,

over conductor C525, `and through contacts M2g A and over conductor C524 to relay I320, or through contactsvMBg and over conductor C523 to relay rFhuseitlier relay-320- or 330 will be ener- 320 operates, closes its holding circuit through -relay 3 l to ground through contacts 2|3 at contacts 322, and closes a circuit from ground through contacts 2id-M13, 323, and 436 to relay #400. Relay-40B operates and opens the holding circuit to magnet M2 through relay yitil at con- -tacts gliel causing them to-restore.

Magnet `M2 inrcstoringremoves a short'circuit from relay Sit contacts MEQ causing it to be energized in series with relay 320. Relay 3|0 operates, prepares a circuit for operating relay 340 at the end .of the next series of impulses at contacts3l2, and sopcns. the circuit to relayililat contacts 13|3 causing it to restore.

B. Tens group selection The next series of impulses received by the connector causes the magnets MI to M to again be operated sequentially in response to successive restorations of relay 200 as previously described. Upon the completion of this series of impulses, relay 440 restores and completes a circuit from ground through contacts 2 I5, over conductor C528, through contacts such as M2h ofthe operated selecting magnet MI to M0, over conductor C521, through contacts 431, 444, `3|2, and 352 to relay 340. Relay 340 operates; closes a circuit to control magnet CM from ground through contacts 2|3, 34|, 36|, and over conductor C5IB; closes its holding circuit through relay 350 to ground through contacts 2 I3 at contacts 342; and closes a circuit to relay 400 from ground through contacts 2I3, 343, 353, and 436. Magnet CM operates and causes the rank selecting member corresponding to the operated selecting magnet to operate. Assuming that the last dialled digit was an 0, Inger F0 will be operated by magnet M0 causing magnet CM to operate rank selecting member RS. Relay 400 operates and opens the holding circuit to magnet M0 through relay 410 at contacts 40|. Magnet M0 restores and removes a short circuit from relay 350 at contacts Mh causing it to be energized in series with relay 340, Relay 353 operates, prepares a circuit for operating relay 360 at the end of the next series of impulses at contacts 352, and opens the circuit to relay 400 at contacts 353 causing it to restore.

It has been assumed in the preceding paragraph that the tens digit was an 0. When the connector is associated with a preceding finder switch instead of a selector it is sometimes desirable that it operate as a selector on particular digits. The present connector is adapted to operate as a, selector when the rst digit received thereby is a 7, 8, 9, or 0, as will presently be described. If the contact sets 1| to 00 are used for trunk service the type of call just described would be completed through a lower numbered contact set. However, due to space limitations, only the contact sets from 3| to 00 have been shown in detail. For this reason it was assumed that the connection described in the preceding paragraph was completed over the 0| to 00 group of contact sets, it being readily understood that the same operations would be involved if the connection had been assumed to be completed-over a lower numbered group.

C. Units selection The third series of impulses received by the connector again causes magnets MI to M0 to be operated sequentially, this time the operation of the corresponding file selecting members FSI to FSB operating the Contact sets 0| to 00 successively since rank selecting member RSO is held operated by magnet CM and finger F0. When relay 440 restores at the end of this series of impulses it extends the control conductor of the called line through the last operated contact set (which will be assumed to be 03), through contacts such as M40, of the selecting magnets succeeding that last operated, over conductor C501, and through contacts 312, 334, 443, 45|, and 434 to relay 310. Relay 440 also completes a circuit from ground through contacts 2|5, over conductor C528, through contacts M372, over conductor C521, and through contacts 431, 444, 3l2, 352, and 331 to relay 360.

10 Relay 330 is rendered slow to operate by means of a copper slug on the armature end of its core. If the called line is busy its control conductor will be grounded causing relay 310 tov operate before relay 333 has time to operate, When relay 310 operates it locks through contacts 434, preliminary make contacts 314, and contacts 2|2 to ground; and connects a source of busy tone through condenser 403, contacts 43|, 31| and through condenser 203 to the calling line extended over conductor C202. When relay 360 operates it opens the circuit to magnet CM at contacts 33|, closes its holding circuit through relay 330 to ground through contacts 2 I3 at contacts 332, and closes a circuit from ground through contacts 2| 3, 363, 333, and 433 to relay 433. Magnet CM restores and rotates shaft 300 oi the latching mechanism to hold iile selecting member F53 independently of magnet M3. Relay 433 operates and opens the holding circuit to magnet M3 through relay 490 at contacts 40| causing them to restore. When magnet M3 restores it removes a short circuit from relay 380 at contacts M3h causing it to be energized in series with relay 360. Relay 330 operates; connects the conductors C50| and C503 (which are multipled to the odd numbered contact sets 0|, 33, etc), to conductors C502 and C504 (which are multipled to the even numbered contact sets 02, 04, etc.) at contacts 33| and 382, respectively; and at contacts 384 transfers conductor C501 from relay 3101y to ground through contacts 313, relay 230, and contacts 2| 2, If the called line is busy the circuit to relay 250 will be open at contacts 312 and 313. However, if the called line is free battery will be extended through the cutoff relay of the called line circuit overv conductor C531, through contacts 312, 334, 313, relay 250, and through contacts 2|2 to ground. Relay 250 operates and closes a circuit to relay 230 at contacts 25|. Relay 230 operates, extends the called line to relay 223 at contacts 23| and 262, shortcircuits relay 250 at contacts 233, and locks to ground through contacts 2 I 2 at contacts 264. Relay 250 restores.

D. Release when called Zine is busy In the event that the called line is busy, relay 313 will have operated to return busy tone to the calling party and to prevent Ythe operation of relays 250 and 230. When the calling party disconnects in response to the busy signal, relay 200 restores and opens the circuit to relay 2li] at contacts 23|. Relay 2|0 restores; removes ground from conductor C204 at contacts 2II to release the preceding switch train; opens circuits to relays 3 I0, 320, 340, 350, and 380 at contacts 2 I 3; and closes a circuit to magnet RM from ground through contacts 213,720I, 2I4, over conductor Clfl, and through contacts 30|. Magnet RM operates and releases the latching mechanism to permit file selecting member FS3 to restore. When the latching mechanism restores, the circuit to magnet RM is opened at contacts 30|. All relays and magnets are now restored to normal.

E. Selecting the ringing code If the called line is idle relays 250 and 260 will have operated as previously described. The calling party then dials a further series of impulsesA to select the ringing code, in the previously selected group, corresponding to the desired party on the called line. Magnets MI to M0 are again sequentially operated but do not affect the contact sets .0l to 00 since rank selecting member ll RSG has'been released by therestoration of magnet CM. Contact set 03 remains operated however since le selecting member yF53 is held operated by the latching mechanism. This latching mechanism is constructed so as not to interfere with the operation of the magnets MI to M0. When relay 440 vrestores at the end of this last series of impulses it completes a circuit from ground through contacts 2|5, over conductor C528, through contacts suchas M271 on the last operated magnet Ml to M0, over conductor C527, through contacts 451, 444, 3i2, 352, 38?, and 422 to relay 420. Relay 420 operates; opens a point in the impulsing circuit at contacts 42|;

.loc-ks to ground through contacts 2|3 at contacts 422; prepares a circuit from ground over conductor 521, through contacts 423, 255, relay 300, and contacts 30| and 32| to conductor C302; and connects conductors C529 and C530 together at contacts 424. These last two conductors are separated prior to the operation of relay 420 to prevent momentary connections between conductors C53| to C540 during overlapping operations of the magnets MI to M0. Each of these latter conductors is intermittently grounded in accordance with two different ringing codes. Conductor C302 is momentarily connected to battery just prior to the transmission of one of these sets of codes over conductors C53| to C540, and conductor C303 is momentarily connected to battery just prior to the trasnmission of the second set of codes over conductors C53| to C540. Conductor 030| is normally connected to battery and is momentarily disconnected therefrom just prior to the start of each code. the rst digit received by the connector determines Which of the two sets of codes is to be used by operating either relay 320 or 330. In the present instance it was assumed that relay 320 was operated, therefore when the battery pulse is received over conductor C302 relay 300 operates over a previously traced-circuit. When relay 300 operates it locks to battery on lead C30| at contacts 30| and connects relay 240 through contacts 302 and over conductor C529, or through A contacts 424 kand over conductor C530, to one of the conductors C53| to C540 through contacts such as M27 on the last operated magnet MI to M0. Relay 240 will be vintermittently operated in accordance with the next code transmitted over the one of the conductors C53| to C540 to which it is connected. As soon as this code is completed battery is removed from conductor C30! by the ringing interrupter. Relay 300 consequently restores and opens a point in the circuit to relay 240 at contacts 302 to prevent operation thereof by the second code transmitted over the one of the conductors C53| to C540 to which it is connected. The same cycle of operations is repeated for each cycle of the ringing interrupter.

F. Signalling the called party Each time that relay 240 operates it transfers the called line from relay 200 to asource of ringing current over conductor C205 and to ground. The side of the called line towhich conductor C205 is connected depends upon whether relay 290 is operated or normal. If the last digit dialed was 1 to 5 this relay will be normal, whereas if the last digit dialed was 6 to 0 a circuit will have been completed from ground through contacts 380, over conductor C522, through contacts M69, and over conductor C52| to relay 290 during the time that magnet M was operated. Relay 250 would then operate, lock to ground through contacts 380 at contacts 293, and reverse the connections As previously described, f,

and 292. ringing current is transmitted over conductor C205, through contacts 292, 242, 252, over conduc tor C503, through contact set 03, over one side of the called line, through the ringers connected to said one vside of the line to ground in case divided ringing is used, or, in case of bridged ringing, through all of the bridged ringers, over the other side of the line, through contact set 03, over conductor C|, and through contacts 25|, 24|, and 29| to ground. When relay 240 is operated it lalso closes a circuit to slow release relay 230 at contacts 242 so Ythat when relay 240 restores it connects the called lineto resistance battery and ground through contacts 23| and 232 during the release time of relay 230 to thereby insure that relay `22|) will not be operated falsely by the charging current of the condensers connected across the line in series with the substation ringers.

When the called party answers, a loop circuit will -be completed to relay 220 causing it to operate and open the holding circuit to the last operated magnet; Ml to M0 in series with one of the relays 410 to 490 at contacts 22|. When this magnet restores it opens the circuit between relay 245 and the one of the conductors C53| to C540 to which it had been connected at contacts such as M27) Yand also opens the circuit to relay 300 at contacts such as M2h, thereby preventing further ringing. The calling party receives transmission battery through relay 200 and the called party receives transmission battery through relay 220. Speech currents are transmitted between the calling and called lines .through condensers 202 and 203.

G. Releasing the connector When the calling party disconnects, the loop circuit to relay 200 is opened causing it to restore and open the circuit to relay 2|0 at contacts 20|. Relay 2|0 restores, removes ground from conductor C204 at contacts 2|| to release the preceding switch train, opens the locking circuit for relay 250 and removes ground from conductor C557 at contacts 2|2 to release the called line equipment, opens circuits to relays 3|0, 320, 340, 350, 350, 385and 420 at contacts 243, and closes a previously traced circuit to magnet RM over conductor C5|0 at contacts 2|4. Magnet RM releases the latching mechanism, the restoration of which opens the circuit to RM at contacts 50|. All relays now restore to normal.

H. Call to a P. B. X. groufp P. B. X. service is provided by strapping the pair of multiple conductors which are extended to conductors C505 and C501, or C555 and C501, by the operation of the crossbar switch contact set corresponding to the first line in the P. B. X. group. The corresponding pairs of multiple conductors for all other lines in the same group, excepting the last line, are strapped through a resistance. Due to this strapping, if the rst line in the called P. B. X. group is busy, the ground extended over conductor C501 from the control conductor of the first line circuit will also be extended over conductor C505, or C505, and through contacts4 44|, or 442 and 44|, 35|, and 383 to relay 430 when relay 440 restores after the third digit has been received by the connector. Relay 430 operates over the above circuit, closes a circuit to relay 4|0 at contacts 432, opens the circuit to relay 310 at contacts 434, shunts contacts 361 .at contacts 4&5 to prevent magnet CM from restoring when relay 366 operates, and opens a point in the circuit to relay 466 at contacts 436. Relay 360 operates as previously described but without effect at the moment. Relay 415 operates; opens the holding circuit to the last operated magnet (which Will be assumed to be M3) in series with the corresponding relay 416 to 436 (in this case relay 496) at contacts 41 1, 412, or 413; closes a circuit to the succeeding magnet M from ground through contacts 432, M4, 415, 433, over conductor C516, and through chain contacts such as M3?) on the selecting magnets; and closes a holding circuit to magnet M3 from ground through contacts 432, 414, 462, 416, over conductor C515, and through chain contacts such as M50 and Mild on the selecting magnets. Relay 415 also locks to ground through contacts 213 and 385 at contacts 414. Magnet M4 operates, locks to ground over conductor C515 at contacts Mec, opens the circuit to magnet 'M3 at contacts Mild, closes a circuit to magnet M5 from ground over conductor C516 at contacts M412, and operates file selecting member PS4 to operate contact set 64. Magnet M3 restores and opens contact set 65. if the second P. B. X. line is busy relay 43E) Will remain energized through the resistance strap between the third and fourth multiple conductors engaged by contact set 64 to ground on the control conductor of the associated line circuit. Magnet M5 will then be permitted to operate and a similar test will be made on the third P. B. X. line. This cycle will continue until an idle line is found or until the last line in the group is reached. In either case the relay 430 will be released and will remove ground from conductor C516 at contacts 453 to prevent further trunk hunting. if relay 435 restores before the last P. B. X. line is reached, battery Will be extended over conductor C501 from the control conductor of the idle line circuit. Ifl relay 436 does not restore until the last P. B. X. line is reached, either battery or ground will be `eX- tended over conductor C561 depending upon whether the last line is idle or busy. In the latter case relay 516 is operated as previously described when relay 436 restores to give the calling party a busy signal. When relay 436 restores it also opens the circuit to magnet CM at contacts 435 and closes a circuit to relay 466 from ground through contacts 213, 355, 358, and 436. Magnet CM restores and rotates shaft S61! of the latching mechanism to hold the operated contact set independently of the selecting magnets. Relay 4136 operates and opens the locking circuit to the operated selecting magnet over conductor C515 at contacts 462. The operated selecting magnet restores and removes ground from conductor C521 thus removing a short circuit from relay 366 and causing it to be energized in series with relay 366. Relay 366 operates and opens the locking circuit to relay 4111 at contacts 385 in addition to its previously described functions. Relay i116 restores. Subsequent operations are the same as previously described for an ordinary line circuit.

I. Call 'to a trunk In certain instances it is desirable that a connector be capable of operating as a selector. For instance, in a small exchange having no selectors, it is desirable that only a single digit be required to reach a trunk to another exchange. he present connector is shown adapted to operate as 14 a selector if the first digit received thereby is 7, 8, 9, or 0. In this event, when relay 448 restores at the end of the series of impulses it completes a circuit from ground through contacts 215, over conductor C528, through contacts such as M511. of the operated selecting magnet Ml' to M6, over conductor C521, through contacts 451, 444, 312, over conductor C526, through contacts such as M139' of the operated selecting magnet M1 to M5, and over conductor C525 to relay 456. Relay 451) operates; extends conductor C561 to ground through relay 285' at contacts 451; closes a circuit to magnet CM over conductor C513 from ground through contacts 213, 211, 315, and 454; closes its holding circuit to ground through relay 466 and contacts 213 at contacts 455; and closes a circuit to relay 496 from ground through contacts 213, 468, 45S, and 436. Control magnet CM operates to operate the rank selecting member corresponding to the operated selecting magnet M1 to M5. Relay 466 operates and opens the holding circuit to the operated selecting magnet and corresponding relay 416 to 691i at contacts 61 causing them to restore. When the operated selecting magnet restores it removes a short circuit from relay d66 at contacts such as Mllg causing it to be energized in series with relay 45E). Relay AEE! operates; substitutes direct ground for ground through a dial tone transformer on the lower winding of relay 266 at contacts 461 (if used); closes ground through contacts 213, 4.66, and 465 to conductor C515; closes ground through contacts 213, 466, 282, and 216 to conductor C516; and opens the circuit to relay 455 at contacts 455. Relay 465 restores. The ground on conductor C515 energizes magnet M1 through chain cone tacts such as M2d on the succeeding selecting magnets. Magnet M1 operates, closes a circuit to magnet M2 from ground over conductor C516 and through chain contacts such as M25 on succeeding selecting magnets at contacts M112, and operates file selecting member F81 to operate the corresponding contact set in the group previously selected by the operation of one of the rank selecting members R51 to RS. If the rst trunk the group is idle, battery will be extended over the control conductor thereof and over conductor C561, through contacts 312, 384, 443, i351, relay through contacts 212 to ground. Relay 26E! then operates and removes ground from conductor C5l6 at contacts 282 to prevent magnet M2 from operating. Ii the rst trunk in the group is busy the control conductor thereof Will be grounded. ,Consequently relay 286 will not operate. Magnet M2 then operates, closes a circuit to magnet M3 from ground over conductor C515 at contacts MSD, locks to ground over conductor C515 at contacts M20, opens the circuit to magnet M1 at contacts M2d, and extends the control conductor of the second trunk in the selected group to relay 28@ over conductor C561. If the second trunk is free relay 236 will operate and prevent magnet M3 from operating by removing ground from conductor C516 at contacts 262. If the second trunk is busy the selecting magnets continue to operate sequentially until an'idle trunk is found or until magnet M6 operates. If an idle trunk is found relay 286 operating Will also close a circuit to relay 215 at contacts 28|. Relay 216 operates; switches the calling loop, extended over conductors C201 and C262, through to the trunk circuit over conductors C551 and C563, or conductors C552 and C564, at contacts 211 and 212; extends the fourth conductor C203 to the trunk circuit over conductor C555 or C566 corresponding to a rank and to a le of said contact sets, lines connected to each of said contact sets, a calling line, means responsive to a series of impulses received over said calling line for operating a corresponding one of said magnets to select a rank of said contact sets, and means operated subsequent to said rank selection for causing said magnets to sequentially operate the contact sets in the selected rank.

10. In a telephone system, a crossbar switch comprising a plurality of separately operable contact sets and two intersecting groups of selecting members therefor, a subscribers line, means responsive to one or more series of impulses received over said line for actuating a member in each group to operate a corresponding one of said contact sets at the intersection of the actuated members, latching means operated to hold the operated contact set independently of said i'lrst means, and means operated under the control of said subscribers line for releasing said latching means.

11. In a telephone system, a crossbar switch comprising a plurality of separately operable oontact sets and two intersecting groups of selecting` members therefor, a subscribers line, means responsive to one or more series of impulses received over said line for actuating a member in each group to operate a corresponding one of said contact sets at the intersection of the actuated members, latching means operated to hold one of said two actuated members to thereby hold the operated Contact set independently of said rst means, and means operated under the control of said subscribers line for releasing said latching means.

12. In a telephone system, a switch comprising two groups of crossed bars, a contact set at each point of intersection of said bars, individual mag nets for operating each bar in one of said groups, a common magnet for operating any bar in the other of said groups, and means responsive to the operation of one of said individual magnets for selecting a corresponding one of the bars in said other group to be operated by said common magnet, a line, impulsing lmeans responsive to a series of impulses received over said line for operating one of said individual magnets, means responsive to the termination of said series of impulses for operating said common magnet to operate the bar in said other group corresponding to the operated individual magnet, and circuit arrangements causing another of said individual magnets to be operated by said impulsing means in response to a second series of impulses received over said line to selectively operate one of said contact sets corresponding to said two successively operated individual magnets.

13. In a telephone system, a plurality of contact sets disposed in ranks and les, a plurality of selecting magnets each corresponding to a rank and to a le of said contact sets, a common magnet, a line, means responsive to a series of impulses received over said line for jointly operating one of said selecting magnets and said common magnet, means responsive to the joint operation of said two magnets for selecting the corresponding rank of contact sets, said first means being responsive to a further series of impulses received over said line to operate another of said selecting magnets, and means responsive to the operation of said other selecting magnet for selectively operating the contact set in the corresponding le and in the previously selected rank.

14. In a telephone system, a plurality of contact sets disposed in ranks and les, a plurality of magnets associated with said ranks and said les of contact sets, each of said magnets being associated with one of said ranks of contact sets and also with one of said les of contact sets, a line, means responsive to successive series of impulses received over said line for successively operating corresponding ones of said magnets, and means controlled by said successive operations of said corresponding magnets for selectively operating a particular one of said contact sets.

15. In a telephone system, a plurality of contact sets disposed in ranks and files, a plurality of magnets associated with said ranks and said files of contact sets, each of said magnets being associated with one of said ranks of contacts sets and also with one of said les of contact sets, a line, means controlled over said line for operating a particular one of said magnets, means responsive to said operation of said particular magnet for selecting the rank of contact sets associated with said particular magnet, said rst means again controlled over said line for reoperating said particular one magnet or for operating another of said magnets, and means responsive to said operation of said last .magnet for operating the contact set in said previously selected rank of contact sets which is in the file of contact sets associated with said last magnet.

JOHN H. VOSS.

REFERENCES CITED UNITED STATES PATENTS Name Date Taylor Oct. 30, 1923 Number 

